Hi, all. I am looking at a 251 cid Dodge Powerwagon six cylinder flathead. I have a 1951 B-3 with a four speed fluid drive transmission. Will the 251 cid engine fit in my truck without alterations and will it mate up with my transmission without alterations. Any input would be greatly appreciated.

I am afraid I can't help you with your question, but I have one for you - What do you use to lubricate your fluid drive? Manual says use only Mopar Fluid drive liquid which of course no longer is made?

My brother has been driving a 1948 DESOTO since 1972. The Chrysler dealer back then told us 5 weight non detergent. We have had no problems in the last 30 years.
I hope this helps.
mrgearhead

PS Look for this oil at the oil warehouses or distributors.

I have a 1949 Chrysler with the 251 flat six and fluid drive. To my knowledge the bell housings are the same and it should bolt on. Did a swap back in the late 60's putting a Plymouth engine in another 49 Chrysler, all done and driving in two days. Plymouth had the regular 3 speed and the Chrysler was Fluid Drive.
You can use "Universal Tractor Fluid #134 in the Fluid Drive without a problem. Second best is Ford ATF Type F Fluid.
Check out this site...scoll to bottom of page for a good atricle on Fluid Drive.
http://www.merc583.addr.com/mopar/framesets/techtipframeset.html
Good Luck